Air conditioning systems are currently commonplace in homes, office buildings and a variety of vehicles including, for example, automobiles. Over time, the refrigerant included in these systems becomes depleted and/or contaminated. As such, in order to maintain the overall efficiency and efficacy of an air conditioning system, the refrigerant included therein may be periodically replaced or recharged.
Portable carts, also known as recover, recycle, recharge (“RRR”) refrigerant service carts or air conditioning service (“ACS”) units, are used in connection with servicing refrigeration circuits, such as the air conditioning unit of a vehicle. The portable machines include hoses coupled to the refrigeration circuit to be serviced. The ACS unit operates to recover refrigerant from the vehicle's air conditioning unit, purify the refrigerant, and subsequently recharge the system from a supply of either recovered refrigerant or new refrigerant from a refrigerant tank.
During the recovery process, there is a need to accurately measure the amount of refrigerant that is removed from the system in order to troubleshoot possible causes of the system failure and also to track the amount of refrigerant used.
Typical ACS units are configured to initiate a “clearing” process prior to a recovery routine to reduce the amount of refrigerant in the ACS unit on the low pressure side of the compressor. This clearing process allows removal of most of the residual refrigerant from the high and low pressure sides of the unit. Removing this refrigerant prior to and following a recovery is important so that the difference between the initial and final weight of the refrigerant tank provides an accurate determination of the amount of refrigerant recovered for the user. The unit uses the compressor and solenoid valves to remove any residual refrigerant that may have been left behind in a previous process. Currently, ACS units measure the removal of the refrigerant by reading a pressure transducer in the low pressure side of the unit while using the compressor and solenoid valves to pull the refrigerant out of the low pressure side of the unit until the pressure is sufficiently low that the amount of refrigerant is assumed to be negligible.
The problem with the prior art clearing process, however, is that the entire quantity of refrigerant cannot be accounted for. The compressor pressurizes the refrigerant pulled from the low-pressure side of the unit and transfers the refrigerant to the high pressure side of the unit. Upon deactivating of the compressor, a small, but non-negligible, quantity remains in the plumbing and chambers in the high pressure side of the ACS unit. Depending on the ambient conditions and the state of the unit prior to the clearing process, the refrigerant remaining in the high pressure side of the unit can substantially affect the accuracy of the determined recovered weight of refrigerant.
Furthermore, the clearing process also requires the ACS unit to have additional solenoid valves and check valves to properly perform the clearing process and enable an accurate determination of refrigerant recovered. The additional valves require more plumbing, wiring, and machining, all of which increase the initial and maintenance costs of the ACS unit. Additionally, the clearing operation requires additional time to complete, adding, in some systems, one minute or more to the length of the recovery operation.
What is needed, therefore, is a refrigerant recovery unit that accurately calculates the amount of refrigerant recovered during a refrigerant recovery process using fewer valves. Additionally, a refrigerant recovery unit that can calculate the amount of refrigerant remaining in the plumbing and chambers of the unit without performing a clearing operation would be desirable.